O2 + Fe3O4 = Fe2O3

O_2 oxygen + FeO·Fe_2O_3 iron(II, III) oxide ⟶ Fe_2O_3 iron(III) oxide

Balance the chemical equation algebraically: O_2 + FeO·Fe_2O_3 ⟶ Fe_2O_3 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 O_2 + c_2 FeO·Fe_2O_3 ⟶ c_3 Fe_2O_3 Set the number of atoms in the reactants equal to the number of atoms in the products for O and Fe: O: | 2 c_1 + 4 c_2 = 3 c_3 Fe: | 3 c_2 = 2 c_3 Since the coefficients are relative quantities and underdetermined, choose a coefficient to set arbitrarily. To keep the coefficients small, the arbitrary value is ordinarily one. For instance, set c_1 = 1 and solve the system of equations for the remaining coefficients: c_1 = 1 c_2 = 4 c_3 = 6 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | O_2 + 4 FeO·Fe_2O_3 ⟶ 6 Fe_2O_3

+ ⟶

oxygen + iron(II, III) oxide ⟶ iron(III) oxide

| oxygen | iron(II, III) oxide | iron(III) oxide molecular enthalpy | 0 kJ/mol | -1118 kJ/mol | -826 kJ/mol total enthalpy | 0 kJ/mol | -4474 kJ/mol | -4956 kJ/mol | H_initial = -4474 kJ/mol | | H_final = -4956 kJ/mol ΔH_rxn^0 | -4956 kJ/mol - -4474 kJ/mol = -482.4 kJ/mol (exothermic) | |

| oxygen | iron(II, III) oxide | iron(III) oxide molecular free energy | 231.7 kJ/mol | -1015 kJ/mol | -742.2 kJ/mol total free energy | 231.7 kJ/mol | -4062 kJ/mol | -4453 kJ/mol | G_initial = -3830 kJ/mol | | G_final = -4453 kJ/mol ΔG_rxn^0 | -4453 kJ/mol - -3830 kJ/mol = -623.3 kJ/mol (exergonic) | |

Construct the equilibrium constant, K, expression for: O_2 + FeO·Fe_2O_3 ⟶ Fe_2O_3 Plan: • Balance the chemical equation. • Determine the stoichiometric numbers. • Assemble the activity expression for each chemical species. • Use the activity expressions to build the equilibrium constant expression. Write the balanced chemical equation: O_2 + 4 FeO·Fe_2O_3 ⟶ 6 Fe_2O_3 Assign stoichiometric numbers, ν_i, using the stoichiometric coefficients, c_i, from the balanced chemical equation in the following manner: ν_i = -c_i for reactants and ν_i = c_i for products: chemical species | c_i | ν_i O_2 | 1 | -1 FeO·Fe_2O_3 | 4 | -4 Fe_2O_3 | 6 | 6 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression O_2 | 1 | -1 | ([O2])^(-1) FeO·Fe_2O_3 | 4 | -4 | ([FeO·Fe2O3])^(-4) Fe_2O_3 | 6 | 6 | ([Fe2O3])^6 The equilibrium constant symbol in the concentration basis is: K_c Mulitply the activity expressions to arrive at the K_c expression: Answer: | | K_c = ([O2])^(-1) ([FeO·Fe2O3])^(-4) ([Fe2O3])^6 = ([Fe2O3])^6/([O2] ([FeO·Fe2O3])^4)

Construct the rate of reaction expression for: O_2 + FeO·Fe_2O_3 ⟶ Fe_2O_3 Plan: • Balance the chemical equation. • Determine the stoichiometric numbers. • Assemble the rate term for each chemical species. • Write the rate of reaction expression. Write the balanced chemical equation: O_2 + 4 FeO·Fe_2O_3 ⟶ 6 Fe_2O_3 Assign stoichiometric numbers, ν_i, using the stoichiometric coefficients, c_i, from the balanced chemical equation in the following manner: ν_i = -c_i for reactants and ν_i = c_i for products: chemical species | c_i | ν_i O_2 | 1 | -1 FeO·Fe_2O_3 | 4 | -4 Fe_2O_3 | 6 | 6 The rate term for each chemical species, B_i, is 1/ν_i(Δ[B_i])/(Δt) where [B_i] is the amount concentration and t is time: chemical species | c_i | ν_i | rate term O_2 | 1 | -1 | -(Δ[O2])/(Δt) FeO·Fe_2O_3 | 4 | -4 | -1/4 (Δ[FeO·Fe2O3])/(Δt) Fe_2O_3 | 6 | 6 | 1/6 (Δ[Fe2O3])/(Δt) (for infinitesimal rate of change, replace Δ with d) Set the rate terms equal to each other to arrive at the rate expression: Answer: | | rate = -(Δ[O2])/(Δt) = -1/4 (Δ[FeO·Fe2O3])/(Δt) = 1/6 (Δ[Fe2O3])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| oxygen | iron(II, III) oxide | iron(III) oxide formula | O_2 | FeO·Fe_2O_3 | Fe_2O_3 Hill formula | O_2 | Fe_3O_4 | Fe_2O_3 name | oxygen | iron(II, III) oxide | iron(III) oxide IUPAC name | molecular oxygen | |

| oxygen | iron(II, III) oxide | iron(III) oxide molar mass | 31.998 g/mol | 231.53 g/mol | 159.69 g/mol phase | gas (at STP) | solid (at STP) | solid (at STP) melting point | -218 °C | 1538 °C | 1565 °C boiling point | -183 °C | | density | 0.001429 g/cm^3 (at 0 °C) | 5 g/cm^3 | 5.26 g/cm^3 solubility in water | | | insoluble surface tension | 0.01347 N/m | | dynamic viscosity | 2.055×10^-5 Pa s (at 25 °C) | | odor | odorless | | odorless